U.S. patent application number 10/922397 was filed with the patent office on 2005-02-24 for power line property measurement devices and power line fault location methods, devices and systems.
Invention is credited to Uber, Arthur E. III, Uber, Bronwyn E..
Application Number | 20050040809 10/922397 |
Document ID | / |
Family ID | 34216078 |
Filed Date | 2005-02-24 |
United States Patent
Application |
20050040809 |
Kind Code |
A1 |
Uber, Arthur E. III ; et
al. |
February 24, 2005 |
Power line property measurement devices and power line fault
location methods, devices and systems
Abstract
A device for use in locating a fault on a power line of a power
distribution system includes: at least one sensor for measuring at
least one property of the power line, and at least one output
device in operative connection with the sensor to signal a state of
the power line. The signaled state of the power line is determined
from the measured property and indicates whether a fault has
occurred in the power line. The output device can, for example,
signal a current state or a previous state of the power line. The
device can further include a controller in operative connection
with the output device to control the operation of the output
device based upon at least one of the current state or the past
state of the power line. A device for use in measuring a property
of power line of a power distribution system includes: a connector
adapted to place the device in operative connection with the power
line in the power distribution system without taking the power line
out of operation; a sensor for measuring a property of the power
line, and an output device in operative connection with the sensor
to transmit a signal representative of the measured property.
Inventors: |
Uber, Arthur E. III;
(Pittsburgh, PA) ; Uber, Bronwyn E.; (Pittsburgh,
PA) |
Correspondence
Address: |
HENRY E. BARTONY, JR.
BARTONY & HARE, LLP
SUITE 1801
429 FOURTH AVENUE
PITTSBURGH
PA
15219
US
|
Family ID: |
34216078 |
Appl. No.: |
10/922397 |
Filed: |
August 20, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60497108 |
Aug 22, 2003 |
|
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|
Current U.S.
Class: |
324/117R |
Current CPC
Class: |
G01R 15/142 20130101;
Y04S 10/522 20130101; Y04S 10/52 20130101; G01R 31/086
20130101 |
Class at
Publication: |
324/117.00R |
International
Class: |
H05B 041/36 |
Claims
What is claimed is:
1. A device for use in locating a fault on a power line of a power
distribution system, comprising: at least one sensor for measuring
at least one property of the power line, and at least one output
device in operative connection with the sensor to signal a state of
the power line, the state being determined from the measured
property, the signaled state indicating whether a fault has
occurred in the power line.
2. The device of claim 1 wherein the output device signals a
current state or a previous state of the power line.
3. The device of claim 2 further comprising a controller in
operative connection with the output device to control the
operation of the output device based upon at least one of the
current state or the past state of the power line.
4. The device of claim 3 wherein said property is the current
passing through the power line.
5. The device of claim 1 wherein the signal of the output device
can be sensed by a human.
6. The device of claim 1 wherein the output device emits
electromagnetic radiation.
7. The device of claim 6 wherein the electromagnetic radiation is
visible light.
8. The device of claim 1 wherein the output device emits sound.
9. The device of claim 8 wherein the sound is in the human audible
range.
10. The device of claim 1 further comprising at least one connector
to position the device in sufficiently close proximity to the power
line to enable the sensor to measure the property.
11. The device of claim 10 wherein the connector is adapted to
connect the device to a power line while the power line is in
operation.
12. The device of claim 11 wherein the connector places the device
in operable connection with the power line via a non-conductive
proximity relationship.
13. The device of claim 11 wherein the connector places the device
in operable connection with the power line via a non-conductive
contacting relationship.
14. The device of claim 11 wherein the connector places the device
in operable connection with the power line via a conductive
contacting relationship.
15. The device of claim 1 further comprising a power source,
wherein at least one of the sensor and the output device is in
operative connection with at least one electrical circuit powered
from the power source.
16. The device of claim 3 further comprising a power source,
wherein at least one of the sensor, the output device, and the
controller is in operative connection with at least one electrical
circuit powered from the power source.
17. The device of claim 1 wherein the sensor measures at least one
of current, voltage, power, temperature, stress, vibration
amplitude or vibration frequency.
18. The device of claim 1 wherein the sensor measure current via a
measurement of the magnetic filed caused by current in the power
line.
19. The device of claim 18 wherein the sensor is a Hall effect
sensor.
20. The device of claim 1 wherein the device provides a signal
indicating whether the power line is powered.
21. A system for use in locating a fault in a power distribution
system, comprising: a plurality of indicator devices, each of the
indicator devices comprising: at least one sensor for measuring at
least one property of a power line in the power distribution
system, and at least one output device in operative connection with
the sensor to signal a state of the power line, the state being
determined from the measured property, the signaled state
indicating whether a fault has occurred in the power line, the
plurality of indicator devices being connected at different points
in the power distribution system such that the signals of the
output devices of the indicator devices enable tracing of the
fault.
22. The system of claim 21 wherein the at least two of the
plurality of devices can communicate between each other.
23. A device to measure at least one property of a power line of a
power distribution system, comprising: at least one sensor for
measuring the property of the power line, at least one controller
in operative connection with the sensor for at least periodically
receiving a signal of the measure property from the sensor, at
least one output device in operative connection with the controller
to signal a state of the power line, the state being determined
from the measured property, and and a power supply rechargeable
from the power line to power the device.
24. A method of determining the location of a fault in a power
distribution systems, comprising: prior to the fault occurring,
placing a plurality of devices in operable association with two or
more branches of a power line of the power distribution system,
wherein each device can determine if a fault current passed through
the associated power line and can provide an indication if a fault
current passed therethrough; subsequent to the occurrence of the
fault, following the power line to the branch point, and following
the power line from the branch point as indicated by the devices to
have indicated the fault.
25. The method of claim 24 further comprising arriving at a
subsequent branch point and following the power line from the
subsequent branch point as indicated by the devices to have
indicated the fault.
26. A device for use in measuring a property of power line of a
power distribution system, comprising: a connector adapted to place
the device in operative connection with the power line in the power
distribution system without taking the power line out of operation;
a sensor for measuring a property of the power line, and an output
device in operative connection with the sensor to transmit a signal
representative of the measured property.
Description
[0001] CROSS REFERENCE TO RELATED APPLICATION
[0002] This application claims benefit of the priority date of U.S.
Provisional Patent Application Ser. No. 60/497,108, filed Aug. 22,
2003, the disclosure of which is incorporated herein by
reference.
FIELD OF THE INVENTION
[0003] The present invention relates to measurement devices for
measurement of power line properties and to methods, devices and
systems for determining the location of power line faults. The
methods devices and systems of the present invention can, for
example, be used by power distribution companies to aid their crews
in more easily and quickly finding power line faults, and, as a
result, better serve their customers.
BACKGROUND OF THE INVENTION
[0004] Electricity is essential in all industrialized countries. It
is used to power everything from small household appliances to
large factories. To deliver electricity to each individual house,
school, hospital or other building, a complex branching system or
network of power lines can be found, usually overhead, throughout
populated areas. These overhead power lines can be disrupted or
knocked down by many things, for example in an ice storm, by a tree
falling as a result of wind or lightening, or because of a vehicle
hitting a utility pole. Because our convenience, livelihood, and
sometimes even individual's lives are dependent upon electricity,
this can lead to a dangerous or costly situation when many people
are left without power for a significant length of time. When a
wire breaks and falls to the ground, contacts an uninsulated part
of the pole or another wire, or if a transformer, insulator or
other piece of equipment fails, the surge of current to ground
causes a circuit breaker to open. The circuit breaker usually tries
to reset itself once or twice, and if it is unable to do so, it
stays off until a repair crew drives to the location, searches for,
finds, and repairs the fault. Power company systems can often
indicate which circuit breakers at which substation are open. But
finding the location of the fault between the substation and the
buildings can be difficult because of the branching nature of power
circuits and the remoteness and difficulty observing some runs of
the power line.
[0005] Currently a power company needs to send out a truck with
line repair personnel. Unless there is a call from a customer
telling them exactly where the fault is located, they have to start
from the power distribution substation and follow the wires out,
looking for the fault, often through all hours of the night and/or
during a storm. This is a very arduous task; all the while leaving
customers without power. It is made more complicated because of the
branching nature of residential power distribution system.
[0006] This was illustrated by a bad storm several years ago in the
south Point Breeze section of Pittsburgh, Pa. A number of trees or
large branches had been knocked down, some blocking streets.
However, not every downed tree harmed the power lines, because in
some areas the power lines are located in alleys or along the
property line between houses, rather than along the streets. One of
the inventors spent several hours helping a power company crew
follow the lines looking for the fault. It was not until several
hours later that the power company crew found the fault, fixed it,
and was able to restore power to the neighborhood.
[0007] There is currently no way to easily retrofit a fault
location device or system to an existing, operating power line.
SUMMARY OF INVENTION
[0008] In one aspect, the present invention provides a device for
use in locating a fault on a branch power line of a power
distribution system including: at least one sensor for measuring at
least one property of the power line, and at least one output
device in operative connection with the sensor to signal a state of
the power line. The signaled state of the power line is determined
from the measured property and indicates whether a fault has
occurred in the branch of the power line. The output device can,
for example, signal a current state or a previous state of the
power line. The device can further include a controller in
operative connection with the output device to control the
operation of the output device based upon at least one of the
current state or the past state of the power line.
[0009] The signal of the output device can, for example, be sensed
by a human. In one embodiment, the output device emits
electromagnetic radiation. The electromagnetic radiation can be
visible light. In another embodiment, the output device emits
sound, which can be in the human audible range.
[0010] The device can further include at least one connector to
position the device in sufficiently close proximity to the power
line to enable the sensor to measure the property. In one
embodiment, the connector is adapted to connect the device to a
power line while the power line is in operation. The connector can,
for example, place the device in operable connection with the power
line via a non-conductive proximity relationship. The connector can
alternatively place the device in operable connection with the
power line via a non-conductive contacting relationship. The
connector can alternatively place the device in operable connection
with the power line via a conductive contacting relationship.
[0011] The device can further include a power source, wherein at
least one of the sensor and the output device is in operative
connection with at least one electrical circuit powered from the
power source.
[0012] The sensor of the device can, for example, measure at least
one of current, voltage, power, temperature, stress, vibration
amplitude or vibration frequency. In one embodiment, the sensor
measures current via a measurement of the magnetic filed caused by
current in the power line. The sensor can, for example, be a Hall
effect sensor.
[0013] In another aspect, the present invention provides a system
for use in locating a fault in a power distribution system
including: a plurality of indicator devices, wherein each of the
indicator devices includes: at least one sensor for measuring at
least one property of a power line in the power distribution
system, and at least one output device in operative connection with
the sensor to signal a state of the power line. As described above,
the state is determined from the measured property and indicates
whether a fault has occurred in the power line. The plurality of
indicator devices are connected at different points in the power
distribution system such that the signals of the output devices of
the indicator devices enable tracing of the fault.
[0014] In another aspect, the present invention provides a device
to measure at least one property of a power line of a power
distribution system including: at least one sensor for measuring
the property of the power line, at least one controller in
operative connection with the sensor for at least periodically
receiving a signal of the measure property from the sensor, at
least one output device in operative connection with the controller
to signal a state of the power line, wherein the state is
determined from the measured property, and a power supply
rechargeable from the power line to power the device.
[0015] In another aspect, the present invention provides a method
of determining the location of a fault in a power distribution
systems including: prior to the fault occurring, placing a
plurality of devices in operable association with two or more
branches of a power line of the power distribution system, wherein
each device can determine if a fault current passed through the
associated power line and can provide an indication if a fault
current passed therethrough; subsequent to the occurrence of the
fault, following the power line to the branch point, and following
the power line from the branch point as indicated by the devices to
have indicated the fault. The method can also include arriving at a
subsequent branch point and following the power line from the
subsequent branch point as indicated by the devices to have
indicated the fault.
[0016] In still a further aspect, the present invention provides a
device for use in measuring a property of a power line of a power
distribution system including: a connector adapted to place the
device in operative connection with the power line in the power
distribution system without taking the power line out of operation;
a sensor for measuring a property of the power line, and an output
device in operative connection with the sensor to transmit a signal
representative of (for example, proportional to) the measured
property.
[0017] In several embodiments, the devices, systems, and methods of
the present invention can quickly and efficiently guide power line
repair personnel to the location of a fault. For example, a device
of the present invention, which is in proximity to a power line,
can indicate whether or not a surge current has passed through that
power line just prior to the power being shut off. The device can
also monitor and communicate other characteristics of the power
line that would be beneficial to the power line company to know.
Likewise, a set of devices of the present invention can be placed
in proximity to a power line along the length of the power line to
indicate the path taken by a surge current that passed through that
section of the line just prior to the power being shut off.
Moreover, one or more of the devices of the present invention can
communicate with other similar devices or another device to aid in
determining the fault location. The devices of the present
invention can further provide an indication of whether a power line
is currently powered to enhance the safety of power line
workers.
[0018] The systems and devices of the present invention are
relatively easy for power companies to install and to monitor. The
sophistication of the monitoring systems can vary depending upon
the power company's needs and willingness to invest in the system.
The systems and devices of the present invention are also
relatively simple to manufacture, distribute, and install at low
costs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other aspects of the invention and their advantages will be
discerned from the following detailed description when read in
connection with the accompanying drawings, in which:
[0020] FIG. 1 illustrates a schematic representation of how
electricity is distributed from a power substation to individual
houses.
[0021] FIG. 2 illustrates a block diagram of an embodiment of the
invention.
[0022] FIGS. 3 and 4 illustrate an outside view of an embodiment of
the invention.
[0023] FIGS. 5, 6, and 10 illustrate details of an actual power
line system.
[0024] FIG. 7 illustrates an embodiment of a sensor for use in the
present invention.
[0025] FIG. 8 illustrates a graph of the behavior of the sensor of
FIG. 7.
[0026] FIG. 9 illustrates a bridging wire between to power
lines.
[0027] FIG. 11 illustrates a block diagram of another embodiment of
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0028] FIG. 1 is a simple schematic of a local power distribution
grid showing how electricity is distributed from a power substation
11 to individual houses 15. The power substation 11 feeds two high
voltage lines, 12a and 12b. The number of lines can vary. Three (3)
is a common number because of the benefits of 3 phase AC power. The
power substation contains circuit breakers that interrupt the flow
of power to the high voltage lines 12a and 12b if the current drawn
exceeds the capacity of the lines or other equipment. High voltage
lines 12a and 12b can be on the order of 13,000 Volts (V) and carry
currents of hundreds of amperes. These lines are on the very top of
the power poles. They branch as needed and periodically are
connected to step down transformers 13. These transformers reduce
the voltage to +/-110 V for use in the home. The output of these
transformers is usually 3 wires indicated as power line 14, a +110
V, a neutral, and a -110 V which run along the power poles below
the high voltage line. Illustrative aspects of actual power line
segments are show in FIGS. 5, 6, 9, and 10.
[0029] In regards to the high voltage lines, 12a and 12b, different
line styles are used in the FIG. 1 to increase understanding, but
the actual wires on the power pole are indistinguishable. This
makes it very difficult to determine which wire branches at a
specific point, making it even more difficult to follow a specific
circuit and wire to check that there is no fault on it. Power lines
12a and 12b may have separate circuit breakers in the substation
11, or they can both be on one circuit breaker, in which case a
fault on either line 12a or 12b will cause the breaker to open.
[0030] When a circuit breaker at a substation detects an over
current condition and opens, it normally notifies the central power
control station. Then after a short period of time, either
automatically or through operator control, the circuit breaker is
closed. If it stays closed, then it is assumed that the fault
cleared itself and power is restored. This is done because there
can be faults that are transient in nature, such as lightening
induced currents or a branch or tree hitting a power line but not
staying in contact with the power line and not breaking the line.
Another source of a transient over current condition is if the
falling tree severed the high voltage power line close to a pole in
such a way that there was a fault to ground while the tree was in
contact with line and falling, but once the tree fell and the wire
was severed, there was then no fault to ground. In this case, the
circuit breaker will close in the on state, and remain on, but
houses served by the section of the power line downstream (from the
substation) of the break will have no power.
[0031] If the circuit breaker detects a continuing over current
condition after being restored, it trips or opens again. Sometimes
there are additional reset attempts. After 2 attempts it is common
to dispatch a crew to inspect the power lines 12a, 12b, and 14,
manually clear or repair the fault, and report in when it is
cleared. Then the circuit breaker can be reset and power is
restored. The power company generally knows a starting point for
the crew to search either because of communications from the
substation or from the pattern of calls to the power company
reporting individual power outages.
[0032] The challenge the power line crew faces is to find the fault
through the many branchings of the power lines. Without an
indicating device there is no way to discern the path taken by the
overload or fault current. For example, as shown in FIG. 1, segment
29 branches into segments 30, 32, and 33. Likewise segment 33
branches into segments 34 and 35. Segment 34a denotes a portion of
segment 34 before the first transformer 13 and segment 34b denoted
the portion of segment 34 from the first transformer 13 to a second
transformer 13.
[0033] FIG. 5 is an illustration of an actual crossing power line
circuit. In this case there are three parallel lines. Bridging
devices 16 couple power from the higher wires for example 29 to 32
to the lower wires, for example 30 to 33 that run perpendicular to
the higher wires. FIG. 6 is a an illustration of a transformer 13
with a bridging connector 16 connecting it to high voltage power
line such as 12a. The transformer's output is the set of 3 wires
described above as power line 14. FIG. 10 is a an illustration of
the power lines several hundred feet down the street from the
crossover of FIG. 6, showing that power line 12a stops in this
direction and power line 12b continues. This corresponds to point
31 in the diagram of FIG. 1.
[0034] FIG. 2 shows a functional block diagram of the device 50 of
the present invention. A sensor 52 measures one or more properties
characteristic of the power line 49 with which it is in functional
proximity. Examples of sensor 52 are a coil of wire, a magneto
resistive sensor, and a hall effect transducer. All of these
measure magnetic fields and thus can measure current in the power
line 49. Exemplary magnetic field sensors are the A1321/2/3 family
of ratiometric linear Hall effect sensors manufactured by Allegro
MicroSystems, Inc., of Worcester, Mass. or the solid state Hall
effect sensors--high performance miniature ratiometric linear SS490
series made by Honeywell of Freeport, Ill.
[0035] The output element 53 can indicate to a person, either
directly or indirectly whether a fault current passed through the
segment of the power line 49 that is being monitored. In one
embodiment, output element 53 could be a red and a green emitting
LED either in one package or packaged separately. The output
element 53 could also be a device that changes color and is viewed
via reflected light. More options are discussed below. Devices
visible in reflected light have the benefit of being more viewable
in daylight. Devices that emit light are better viewed in the dark.
A single device 50 could include both types.
[0036] Controller 51 monitors the sensor 52 and determines when to
activate one or any of several output devices 53 based upon the
sensor input and a sequence of events in time. A series of
activation states or sequences and options are discussed below.
Controller 51 is preferably a microprocessor, although it can be
partially or totally a mechanical device where some or all of the
logic is carried out in mechanics rather than in electronics.
Similar to how a mechanical circuit breaker works, an over current
would trip the indicator device 50 and a "flag" would show. When
the power comes back on with a current below the trip current, the
flag would be retracted or reset so that it is no longer visible.
If electronic, controller 51 is preferably a simple one chip
microprocessor system such as are manufactured by a myriad of
companies, but it can also be an analog or mixed circuitry device.
Some or all of the circuitry can be embodied in a custom integrated
circuit, which can significantly reduce the per piece cost of the
electronics. These are among the many functional options useable by
an electronic designer skilled in the art.
[0037] If the controller 51, sensor 52, or output element 53
incorporate electronic elements, then a source of electrical
energy, power source 54, is needed. Power source 54 could be a
coil, rectifier, and capacitor that taps power from the power line
without conductive contact. If the power line indicator device 50
needs to operate when power line 49 is de-energized, power source
54 then needs to incorporate a battery, large capacitor, or other
device for storing energy so that it can be released as electrical
energy when the power line 49 power is off. Power source 54 could
beneficially include a device to recharge the power storage device.
This could be a coil and rectifier to pick up power from the power
line 49, a solar cell, a thermoelectric energy source, or a device
that generates energy from wind or other motion. With recent
improvements in battery technology, lower power electronics, and
LED efficiency, it might be possible to incorporate sufficient
battery power in the power line indicator device 50 that it can
last for its expected lifetime. Then no recharging capability is
needed. This may reduce the initial cost and ensure that there are
continued sales. It also forces the replacement of devices which
otherwise could become old and fail without anyone knowing that
they have failed. While power source 54 is shown connecting
directly only to controller 51 in FIG. 2, it should be recognized
that the power source can be directly connected to all or any of
the electronic elements as needed.
[0038] FIGS. 3 and 4 are side and front external views of one
embodiment of a power line indicator device 50. The device 50 can
be generally thought of as 1.5 revolutions of a flattened or oval
spiral or corkscrew, with a heavier bottom than top. When hanging
on a power line, the two arms 62 and 63 hang on a power line 49
that goes through hole 61. To install the power line indicator
device 50 onto a power line, it is held on the bottom by an
insulated gripper and the power line is inserted all the way into
the slot 60 shown in FIG. 3. With the arms 62 and 63 clearing the
power line, the power line indicator device 50 is rotated 90
degrees so that the power line is passing though the bottom of hole
61. The indicator device 50 is then lowered so that it hangs on the
power line and it is released from the gripper. The dimensions of
the power line indicator device openings 60 and 61 and the length
of the arms 62 and 63 can be adjusted for various cable sizes, or
it be large enough to fit most cables. The arms could narrow toward
the top of opening 61 so that they grip the power cable relatively
tightly. They could also have a rubberized or friction enhancing
texture to reduce the tendency of the indicator device 50 to slide
down a line.
[0039] In one embodiment, the output device 53 is located on the
outside of device 50 while the other components, sensor 52,
controller 51, and optional power source 54 are located internally,
preferably in section 64 where their weight ensures that the power
line indicator device 50 hangs with the output device 53 pointing
downward for easy viewing by a person on the ground. In another
embodiment, the output device 53 can be internally located and when
illuminated it makes the whole indicator device 50 glow. The power
line indicator device 50 is preferably fully weather proof. One way
to do this is to pot all the components inside an opaque epoxy,
which makes a weatherproof seal with the case of the output device
53. Alternatively, some or all of the indicator device 50 could be
translucent or clear so that the light from the output device 53
causes the indicator device 50 to "glow" as mentioned above. Then
the output device 53 could be embedded inside the potting compound
or case of the indicator device 50. The power line indicator device
50 could be insert molded or ultrasonically welded into a housing.
Polycarbonate is a preferred injection molded housing material
because of its toughness. There are also many options for the
housing design. The housing could be similar to a clip clothespin
that is manually opened or opens as the indicator device is pushed
onto the power line and then has a spring which closes it and
maintains its grip on the power line. The clothespin housing can,
for example, be put into the end of an insulating pole that holds
it in the open position. The open end of the clothespin can have a
hook, so that when the power line indicator device 50 in place onto
the wire, the insulating pole can be moved downward, releasing the
clothespin and letting it close onto the power line. A different
end arrangement on the insulating pole could hold and squeeze the
ends of the clothespin, opening the gap and allowing removal from
the wire. Alternatively the housing could use a spring-loaded latch
of any type, such as a carabineer. Again, it could be manipulated
via an insulating rod to place it on or off of the power line. The
device similar to that disclosed in U.S. Pat. No. 5,729,872 can,
for example, be used. A ratchet locks the capture mechanism in
place. A ratchet locking cable tie type mechanism could also be
used. Many of these have the benefit that there is a squeezing
force by the power line indicator device 50 on the power line 49.
This reduces the tendency for the indicator device to move along
the length of the cable 49. In all these embodiments, one or more
sensors 52, controllers 51, output devices 53 and optionally power
sources 54 could be arranged so that they can be easily attached to
or hung from a power line 49, and be readily viewed from the
ground.
[0040] To prepare a power line to be monitored by a plurality of
power line indicator devices 50, the power line indicator devices
50 are installed as described above at various points along long
straight runs of power line such as segment 29 so that a crew can
see from one to the next either with the unaided eye or with
binoculars or night vision scopes. This is especially important if
it is not possible for a power line crew to easily visualize or
follow a power line as it crosses property away from roads or
alleys. It is also important to install power line indicator
devices 50 near or at a branch point such as power lines 30, 32,
and 33 which branch from power line 29 in FIGS. 1 & 5 so that
the crew knows whether to follow one branch or follow the other
branch. Similarly, indicator devices 50 could beneficially be
installed on the output of step down transformer 13 and the power
line segment after the transformer, for example segment 34b.
Although most low voltage power line runs 14 are relatively short
in length, in rural areas, these may cross difficult terrain and
thus could benefit from having periodic power line indicator
devices 50 installed.
[0041] Before discussing operating modes, it is useful to discuss
various power line characteristics and sensors 52 that can be used.
Current conducted through the power lines was mentioned above.
Current can be readily measured with Hall effect sensors or coils
that measure the magnetic field caused by the current. Other
magnetic field sensors may be used. A second characteristic that
can be measured is voltage. Voltage can be measured capacitively,
with two electrodes at different distances from the power line. The
voltage between the two capacitively coupled electrodes depends
upon the electric field between them. Alternatively the power line
indicator device 50 may have a connection to ground or another
reference, optionally a second indicator device 50, allowing it to
measure voltage. This second indicator device 50 can be on a second
power line, on the power pole, or a known distance from the power
line and ground. There are other electric field and voltage sensing
methods that also can be applied as one skilled in the art would
know. In addition, other characteristics of the power lines, such
as temperature, stress, and vibration amplitude or frequency could
be measured and used in the operating algorithm, or just sensed and
transmitted to the power company monitoring system. Temperature is
a particularly useful one to monitor, because the overheating of a
line or transformer could be an indication of line deterioration
and could lead to line sagging. Fiber optic sensors may
preferentially be used for all the above measurements. In this
case, the sensor is all that needs to be in proximity to the power
line and the other components of the indicator device 50 could be
located some distance away, for example anywhere on the power line
pole. In this embodiment, a single indicator device 50 may use one
or more than one sensor 52. These sensors 52 may be in the same
physical package, or may communicate their information to the
controller through a hard wired (for example conductive wire or
fiber optic link) or non-wired linkage (for example RF, IR, or
sonic). Sensors 52 similar to or identical to those disclosed in
U.S. Pat. Nos. 5,426,360 and 6,555,999 B1 can also be used in the
present invention.
[0042] There are many operating modes or operational algorithms
that can be employed in the indicator devices 50 of the present
invention. One or more than one operating mode can be used at the
same time. One is to have the power line indicator device 50
monitor the current passing through the line. The current will
fluctuate as the loads (current demands) from the houses and
building change over time. Turning on lights, refrigerators,
heaters, or central air conditioning will increase the load. If
power goes off, and there has been no current measured above a
specific predetermined threshold, then the controller 51 activates
the output device 53 and the indicator device 50 starts, for
example, flashing green, with one flash every ten (10) seconds. If
there has been a current above the predetermined threshold, then
the controller 51 activates the output element 53 to, for example,
flash red, with one flash every two (2) second. The number of
flashes, each about 1/3 second apart, can, for example, indicate
the number of times that the substation tried to close the circuit
breaker and failed. The output element 53 continues flashing this
way until power is restored, or if the battery starts running low
on charge, it slows the rate down to conserve battery life. One
reason for the different flash rates is to allow a person with
red/green color blindness to notice the difference. An alternative
is to use red and blue LEDs, although blue LEDs are currently more
expensive.
[0043] Several benefits of the devices and system of the present
invention are discussed below in connection with FIG. 5. The power
line indicator device 50a on power line segment 29 is blinking red,
indicated by its black color in the FIG. 5. This indicates that the
fault current passed through that indicator device 50a. The only
other one that is blinking red is indicator device 50b on segment
33. Indicator devices 50c, 50d, and the other indicator devices are
flashing, indicated in FIG. 5 by their clear outline. The power
line crew knows to follow segment 33 and does not need waste any
time checking in any other directions. The power line crew can
follow the indication of the fault path to the location of the
fault. Without the red flashing indicator devices 50a and 50b, the
power line crew would only have had a 33% chance of going the right
way, and at each branching points the odds that they are going the
right way to find the fault get lower and lower.
[0044] If power comes on briefly, but does not stay on, then the
flashing is not stopped and the indicator device 50 is not reset.
If it comes on for a predetermined length of time, for example 1
minute, then the flashing stops and the indicator device 50 returns
to the monitoring state. Alternatively, it may be beneficial for
the flashing to continue up to 12 hours, optionally at a lower
repetition rate, in case there is a broken line down stream of the
indicator device 50, but it was a self clearing fault, for example
a broken line, that still requires efficiently guiding a repair
crew to the location to repair the broken line.
[0045] One difficulty with the algorithm or mode of operation
described above is that the controller 51 makes its decision based
upon a predetermined fixed threshold. This means that there needs
to be different indicator devices 50 for different capacity power
lines. While simple to design and build, fixed threshold devices
increased the inventor for the manufacturer and the power company,
unless the threshold can be set at the time of installation. And
the different indicator devices 50 need to be coded or readable as
to their threshold setting.
[0046] An alternative embodiment is to have the sensor 52 interface
to the controller in a way that covers many orders of magnitude. An
example of this is to have a logarithmic amplifier on the Hall
effect sensor. A second option is to have a series of amplifiers
with gains of, for example, 1, 8, 64, and 512. The controller 51
simply reads all the amplifiers'outputs, using the one that is not
saturated or approximately zero. In this way, the sensor 52 and
controller 51 can accommodate a wide range in the characteristic
being sensed. Another alternative is to have the controller 51 or
sensor 52 incorporate a variable or programmable gain and/or
variable offset stage so that it can adjust itself either
independently or as commanded by the controller 51, so that it can
operate in the correct range for the power cable on which it is
placed. Still another alternative is to have several sensors 52
which differ in their sensitivity, and the controller 51 utilizes
the one that is operable under the conditions in which it finds
itself. Having 3 coils, one with 100 turns around an area of 1
cm.sup.2, a second coil with 1 turn and an area of 1 cm.sup.2, and
a third of 1 turn and an area of 1 mm.sup.2 allows about 5 or 6
orders of magnitude of current to be sensed. Another approach is
discussed in relation to FIGS. 7 and 8. FIG. 7 shows a coil 80 with
diode snubbers or voltage limiters 81 and 82 and outputs or
measurement points 84 and 85. If the coil 80 does not have
sufficient internal resistance, then resistance can be added in
series with the coil 80. FIG. 8 shows the voltage between
measurement points 84 to 85 with different amplitudes of voltage
induced by the magnetic field of the power line. For low fields,
the amplitude of the waveform is a measure of current, curves 95
and 96. For high fields, the limiters 81 and 82 limit the amplitude
of the voltage, but the rise or fall time is shorter the higher the
magnetic field and thus the higher the induced voltage, as is shown
in curves 97, 98, and 99. In this case, the rise time becomes a
measure of the amplitude of the induced voltage, thus the magnetic
field and thence the current in the power line. This allows
measurement over a much wider dynamic range. It is reasonable to
assume that 10 mV to 0.7 V amplitude can be easily measured. This
gives a dynamic range of 70. If the amplitude can be measured down
to 1mv, then the dynamic range is 700. Thereafter, the rise or fall
time can be reasonably be measured from 10 millisecond down to 1
microsecond. This gives an additional dynamic range of 10,000.
[0047] In addition to having the controller 51 decide that a
current is an overload based upon a fixed threshold as discussed
above, the controller 51 could make the decision if the current
increase by a prespecified percentage over the course of one or a
few cycles of the 60 Hz power or a predetermined time if the power
line is carrying DC current.
[0048] Another more flexible algorithm has the controller 51 self
adjust the trigger threshold. When the indicator device 50 is put
on or near a line 49, the controller sets the threshold to be a
small or modest percentage above the current that it sees while the
power stays on. Thus it sets its threshold based upon the "normal"
current. If the current increases for several cycles but does not
trip a circuit breaker, then the threshold is increased. It would
be desirable for the controller 51 to use some time weighted
average or other adaptive algorithm so that the threshold value can
adjust downward as well as upward to normal usage patterns and
still be sensitive to fault currents.
[0049] If the indicator device 50 has the ability to sense both
current and voltage, then it can differentiate out of phase current
from in phase current as well as the direction of power flow. This
can be useful to help the indicator device 50 differentiate a surge
of current flowing toward a fault to ground downstream from the
indicator device 50 from a surge of current from one or more energy
storage devices downstream of the indicator device 50 (motors or
capacitor banks for phase adjustments are examples of such a
device) that can send power back upstream over the grid to a fault
to ground. For this approach, the indicator device preferably has
two sensors 52, one that measures current and a second that
measures voltage. The indicator device 50 now is orientation
dependent so that it's mounting on the power line is important. For
example, the indicator device could be designed so that leg 62 in
FIG. 3 should be on the side of the power line closest to the
substation 11 and leg 63 should be on the power line away from the
substation. The controller 51 can then determine if the current is
in phase with the voltage or out of phase with it, and whether the
power is flowing toward the substation (and thus is coming from
energy storage devices toward a fault) or is going from the
substation and thus most likely toward the fault to ground.
[0050] The output device 53 can be one or several of many options.
For human sensing or reading, it can be a simple light or light
emitting diode that could vary in color and or flashing patterns
depending on the fault conditions. It could emit IR light for
viewing with night vision goggles. It could transmit data in Morse
or some other code. It can be a liquid crystal display (LCD) or
other display that can be seen with reflected or transmitted light.
Any visible distinction between two or more states may be used, for
example color, intensity, time pulsation, or position. The output
device could have a dark disc or plate behind it so that there is
more visible contrast when observed in daylight. Also, for use on
power wires or lines 49 remote from roads, the output element 53
could point to one side to be viewed from the most readily
accessible site or up for viewing by a helicopter. If the whole
indicator device 50 glows as mentioned above, then it can be seen
from all angles. The trade-off is that because the light leaves at
all angles, it is not as bright at the most likely viewing angle.
To overcome this, output element 53 could be bendable so it can be
positioned just before or after it is installed on the power line
49.
[0051] Another human sensible output device 53 can employ sound in
all its variations to alert a user. A challenge is that the ears
cannot isolate the directionality of sound as well as the eyes can
differentiate light, so it might be difficult to determine which of
three indicator devices at the top of a pole is signaling, unless
each had a distinctive sound, in tone or timing. A highly
directional microphone could be used to determine which output
device 53 is operating, and to detect the sound over a greater
distance. The third remote human sense, smell could also be used,
but it is even less directionally reliable than sound, being
carried by the wind. The output element 53 could heat a fluid that
gives off a smell or smoke. Alternatively, it could have a small
electrochemical cell that generated hydrogen sulfide.
[0052] In other embodiments the output device can include output in
segments of the electromagnetic spectrum or sonic spectrum that are
not sensible to humans but can be sensed by electronic equipment.
This has the benefit that a blinking red or green light on the
power line will not alarm bystanders. This also has the benefit
that more information can be encoded in the data stream. Examples
with such desirable characteristics are infrared light or
ultrasonic transmissions. These would be relatively near field
communications methods, good for tens to hundreds of meters.
Electromagnetic or radio waves, either transmitted directly through
the air, as cell phone transmissions, or transmitted over the power
line wires could also be the output of output element 53. These
device to device communications could also employ light or sound
that can be sensed by humans, but still encode data in a way that
is not intelligible by humans. For example the LED could flash at a
rate people cannot see and transmit via pulse code modulation or
Morse code the current on the line while power is still running.
This could be sensed and decoded by a device on the truck or held
by a member of the power crew. This and similar embodiments give
significant additional information to the power company that it
cannot access except through very laborious means at this time.
[0053] In addition, the power line indicator device could include
an input device 55 as shown in FIG. 11. This input device could
receive various communications and the controller 51 would change
state or act appropriately depending upon the communications it
receives. More on this will be discussed later.
[0054] Given the capability for two way communications with an
indicator device 50 or between two or more indicator devices 50, a
significant range of possibilities is available. Each indicator
device 50 or controller 51 could have a unique identifier. Each
indicator device 50 or controller 51 could optionally have a real
time clock and memory that enable it to record events or data and
their time of occurrence for later transmission and analysis. If
the indicator devices 50 can communicate to the central power
company, and the central system knows where every indicator device
50 is located, then the central system can direct the field crew
immediately to the segment where the fault has occurred. The
location of the fault could thus be indicated on the computerized
map of the streets and the power line in the crew's truck. If the
indicator device 50 has both current and voltage measurement
capability it could act as a power meter and load factor monitor
for the associated power line. It could also act as a collector and
repeater of remoter residential or commercial power meter
reading.
[0055] In some of these embodiments, it is important that power
always be supplied to a component or function, for example a
volatile memory. In these cases, there may be several independent,
separable, or somewhat independent power sources 54. If the output
element 53 can deplete the stored energy and deprive the controller
51 of power, then the controller looses the ability to remember its
state and threshold, which is not desirable. Alternatively, for
memory, a non-volatile memory could be used. And, in some instances
it is still desirable to have partitioned power sources, for
example so that RF communications can be heard and made, even if
visible communications cannot be.
[0056] These communications could be in reply to a query from a
human or from the central base or at a time based upon the real
time clock. They could be triggered by the occurrence of a fault.
Alternatively, they could be ongoing from indicator device 50 to
indicator device 50. This is similar to the networking that
commonly occurs between computers in many situations today. There
are many types and architectures of networks in use, for example
hard wired, fiber optic, wireless RF, and wireless infrared. This
could use the most basic and reliable protocols and strategies
because the data rate can be very low. The X-10 communications
protocol that is designed to allow central and remote control of
remote devices over home wiring is one protocol that could be used.
An indicator device 50 can wait to be polled, or it can communicate
periodically. Well known collision avoidance or detection
strategies can be utilized for these periodic communications.
Techniques being developed by International Broadband Electric
Communications of Huntsville, Ala. could also be used to transfer
information from one indicator device 50 to another or to a control
center. With any form of communications to a control center, the
power line crew can be directed right to the indicator device 50
that is closest to the fault, saving time over having to manually
follow the indicator devices 50 from the substation to the fault
location.
[0057] When an indicator device 50 can communicate to another
indicator device 50, especially if over the power line itself, they
can continually be communicating with each other to make sure that
there has not been a break on the line and that all the indicator
devices 50 are functional. If there is a break, the transmission
between adjacent or nearby indicator devices 50 will cease even if
an overcurrent fault has not occurred. If indicator devices 50 were
placed after each step down transformer 13, as well as at branching
points, the communications between them could be used to indicate
if a transformer overheats and its circuit breaker trips, or if it
otherwise fails without causing a high current and tripping the
upstream circuit breaker. The indicator device 50 located upstream
of the open circuit would sense that it is missing transmissions
from the adjacent down stream indicator devices 50 and relay this
failure condition through the other upstream indicator devices 50
to the power substation or otherwise communicate it to the power
company central office so that appropriate action could be taken to
check and restore power to those downstream of the open circuit.
Alternatively, the indicator devices 50 from the fault to the
substation could then their output elements 53 to lead the power
line crew to the location of the break in the line. If a single
indicator device 50 fails, then it could mimic an open line,
although the communications method can be chosen so that it is
possible for the indicator devices 50 to communicate through one
another so that several down the line can be "heard" if the line is
not opened, whereas a number of indicator devices 50 would be
"silenced" if a wire, circuit breaker or transformer were open.
[0058] With multiple indicator devices 50 communicating to each
other, they could all be peers, having the same hierarchical
position, or the selected ones could be masters and run a more
sophisticated operating algorithm. Other information technology or
network structures can be used, as are know to those skilled in
that art.
[0059] The functions of the power line indicator device 50
described herein can be partitioned somewhat arbitrarily between
the sensor 52, controller 51, output element 53, and input device
55. For example, scaling of measurements can be done in the sensor
52 with a digital number reported to the controller 51, or the
sensor 51 can output one or more voltage waveforms as discussed in
connection with FIG. 7, and controller 51 then includes an analog
to digital converter that derives a digital number from the analog
input. Similarly, sophisticated communications protocols such as
those used in cell phones can be utilized fully within input
element 55 and output element 53, or both of these may be embodied
in a single electronic or integrated circuit. Multiple sensors 52,
controllers 51, output elements 53, input elements 55, and even
power sources 54 may be in single indicator device package or may
be functionally linked even though in separate packages. One
beneficial partitioning would be when there are several power lines
49 in parallel. There could be a sensor 52 for each line and just
one controller 51 and one output device 53 where the output is
coded to indicate which line has the fault. Various partitionings
selected by designers skilled within the art are within the scope
of this invention.
[0060] Likewise, a number of mounting options are described herein.
The key is that the power line indicator device be close enough to
measure the necessary characteristic and to indicate which power
line to follow to the fault. The indicator device 50 can hang on
the wire, be mounted or hang on the pole or other existing or new
support in close proximity to the wire, be a part of a support
insulator, be a part of a bridging connector 16 or be built into a
bridging wire 17 or connector hardware 18 shown in FIG. 9, be built
into a transformer, be incorporated in or onto anti-resonance
mechanical devices used on long lengths of power line, or be built
into the power line itself. Connector hardware 18 includes an
attachment element such as a ring 19 which can be used to attach an
extending rod (not shown) that can be used by a worker to safely
maneuver connector hardware 18 in relation to a power line 30 to
attach or remove connector hardware 18 from the power line 30. An
indicator device 50 can beneficially be used at the end of a power
line run to indicate if an open has occurred and optionally to
indicate the number of reset attempts received, as mentioned
elsewhere. Part of the output element 53 could be a fiber optic
cable that is mounted on and runs some distance down the pole to be
more easily seen from the ground. The indicator device 50 in some
embodiments can make electrical contact with the power line or
cable 49 to obtain more accurate information.
[0061] Because the power line 49 will move under the influences of
wind and temperature, the power line indicator device 50 preferably
needs to incorporate designs or strategies to avoid false signals
caused by relative motion of the indicator device 50 and the power
line 49. Some of the rigid mounting options described herein are
sufficient. Also, the package designs that involve grabbing and
holding the cable overcome this to a large degree. One way to
improve all these designs is to incorporate a magnetic material
either inside the case or use magnetic material loaded plastic for
some of the case. This magnetic circuit conducts the magnetic field
to the sensor in a way that makes it less susceptible to errors
from relative motion between the power line 49 and indicator device
50. An exemplary current sensor with a magnetic circuit to make
sensing independent of specific wire position is a CSLA1CD made by
Honeywell of Freeport, Ill. It uses a magnetic material to conduct
magnetic flux to a gap containing a Hall effect sensor.
[0062] The spring loaded or ratcheting closure styles of case are
preferable for use with magnetic loaded plastics because the
closure reduces the air gap in the magnetic circuit. One method of
adjusting the sensitivity of a power line indicator device 50 is to
place non-magnetic shims or pieces into the region of the magnetic
path that closes as the power line is gripped. Widening the gap in
the closed magnetic path reduces the sensitivity.
[0063] For the spiral power line indicator device 50 shown in FIGS.
3 and 4, additional stability can be achieved by having more turns,
for example 2.5 instead of 1.5 mentioned above. Such an indicator
device 50 could not be installed as discussed above, but could be
installed by placing it adjacent to the line at a shallow angle and
"screwing" it onto the line. Another strategy is to have the legs
62 and 63 be wide, extending into and out of the plane of the
drawing in FIG. 4 so that the contact grove with the power line is
lengthened. This would prevent twisting of the indicator device 50
in relation to the power line 49.
[0064] The embodiments above have been discussed in relation to
outside, overhead power lines. Similar benefits would be gained by
using them with in-ground power cables. These are not as likely to
develop faults, however, when they do, it can be very difficult to
identify the segment containing the fault. In this case, the power
line indicator device 50 could be placed or buried in proximity or
contact with the line, and a fiber optic or other output brought to
the surface so that a crew can determine where the fault occurred
that triggered the opening of the circuit. Or, indicator devices 50
could be placed in junction boxes. The power line indicator device
50 would also be helpful within a factory or other installation.
Where there are external power lines, the application is identical
to that described elsewhere herein. Within a building, while the
distances are not as great, and the falling of trees is not likely,
overloads can occur for other reasons. Similarly, these could be
used in household wiring systems, even built into outlets, light
switches, junction boxes or other components, to indicate which
device triggered an overload. In a residential setting it is much
more likely that it is the sum of several loads, each of which is
below the limit for the circuit, caused an overload, however there
is still value in identifying what caused the peak or increase that
triggered the circuit breaker. The power line indicator devices 50
could lead to the offending outlet and this appliance--figuratively
leading to finding the straw that broke the camels back. And these
devices and methods can apply to DC as well as AC power. Hall
effect sensors can measure DC magnetic fields. For example, one
place they can have application is in large communications network
centers where there is significant DC power distribution.
[0065] In addition to indicating faults and other uses mentioned
above, the indicator devices 50 could improve safety for power line
workers by indicating when a power line is electrified or has
significant induced currents. To perform this function, the output
device 53 could be continuously lit when power is sensed, or give a
periodic chirping sound that can be hear when near to it.
[0066] Although the present invention has been described in detail
in connection with the above embodiments and/or examples, it should
be understood that such detail is illustrative and not restrictive,
and that those skilled in the art can make variations without
departing from the invention. The scope of the invention is
indicated by the following claims rather than by the foregoing
description. All changes and variations that come within the
meaning and range of equivalency of the claims are to be embraced
within their scope.
* * * * *